Among conventional work machines in which an engine drives a hydraulic pump and pressure oil discharged from the hydraulic pump operates a hydraulic actuator for a work machine, there are machines in which unnecessary idling of the engine is stopped. For example, Patent Document 1 discloses stop of idling of the engine after a state without an operator in a cab has continued for a predetermined time. With these work machines, it is possible to reduce a fuel consumption and an amount of carbon dioxide to be emitted.    Patent Document 1: Japanese Patent Application Laid-Open No. 2002-13425